Outline of a Produce-Dominated Diet and Why We Need to Cook Vegetables

By Don Matesz, MA, CH, CNC

In my last column, I wrote: "A healthy dietary acid-base balance is obtained when salt sources are minimized and fruits and vegetables form about two-thirds to three-quarters of the diet by weight." Unless you are familiar with the weights of common foods, that may seem like an insurmountable pile of fruits and vegetables.

In reality, it is not.

In a meal composed of about 100 grams each of beef brisket, sweet potato and steamed broccoli, two thirds of the total weight is vegetables. If you add 100 grams of blueberries for dessert, three-quarters of the total weight is fruits and vegetables. These servings are not very large:

a beef brisket about the size of a deck of cards;

a 5" x 2" sweet potato;

about two-thirds of a cup of steamed broccoli; and

about two-thirds of a cup of blueberries.

Many people regularly eat some meals similar to this - meat, potatoes and vegetables - but with larger servings of meat and bread.

As outlined, this meal supplies only 398 calories, but most people would enjoy more fat. Many natural fats can be used, but for simplicity, I calculated adding two teaspoons of unsalted butter (one on the sweet potato, one on the broccoli) and four tablespoons unsweetened cream (on the blueberries). With these additions, the meal has 506 calories - less than one-third the daily requirements of a healthy, moderately active adult female. In other words, the typical modern American woman could eat meals with this design (varying the specific foods) three times daily and consume only about 1,500 calories. For many, that would be a path to gradual fat reduction. A larger or more active person would eat more of everything, in proportion, or use more fat.

Are you afraid you can't get enough fiber without grains, or alternatively, that so much produce provides too much fiber? This meal provides nine grams of fiber; three such meals daily would supply 27 grams. The American Dietetic Association recommends 20-35 grams of fiber daily. Hunter-gatherers free of gut diseases have consumed 100-150 grams of fiber daily from wild fruits and vegetables.

There is a noteworthy difference between fruit and vegetable fibers and cereal fibers. Fruits and vegetables come from dicotyledonous plants, whereas cereals are derived from monocotyledonous plants. The major portion of fiber in fruits and vegetables is soluble, and in the forms of pectins, gums and hemicelluloses, whereas the major portion of fiber in cereals is insoluble, in the form of lignified (i.e., woody) cellulose.

These fibers have different properties. Soluble fibers delay stomach emptying and the transit of chyme through the intestines, increasing time for nutrient absorption and lowering cholesterol. In contrast, insoluble cereal fibers accelerate transit and bind with important nutrients, reducing absorption.

Phytic acid in cereal fibers reduces assimilation of critical minerals, such as calcium; magnesium; iron; zinc; and copper. Humans can't really adapt to phytic acid, and high cereal-fiber diets have been found to cause mineral deficiencies. Moreover, cereal fibers reduce cereal protein assimilation. This is probably why many Chinese physicians say white rice is more digestible than brown rice. The human gut appears much better adapted to fruits and vegetables than whole grain cereals.

What about cooking? Westerners commonly believe raw vegetables are more nutritious than cooked, but Chinese nutrition has long stated the opposite. Who's right?

All of the nutrients in vegetables are locked inside cells composed of fibers. These cells are not opened by chewing, no matter how vigorous, and unlike apes and other herbivores, humans have no enzymes or special gut chambers (e.g., multiple stomachs, enlarged colons) with resident symbiotic protozoa or bacteria for digesting fibers. Consequently, we really can't access the nutrients in raw plant food.

Cooking explodes plant cells, releasing their nutrients. Even though cooking may destroy some nutrients, studies have shown that we absorb more total nutrients from cooked vegetables. We absorb only 1 percent of carotene from raw carrots, but 5 percent to 19 percent from cooked carrots. The softer the texture, the better the absorption. (Similar considerations apply to meat.)

All known cultures, including hunter-gatherers, cook food. In fact, anthropologist Richard Wrangham, of Harvard University, says "living humans appear incapable of surviving on raw foods in the wild." Archaeological evidence indicates humans have been cooking for 1.9 million years (63,000 generations) or more. Our digestive system is adapted to cooked food.

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